The air quality in Chicago has improved after days of unhealthy conditions due to smoke from Canadian wildfires — but the area isn’t entirely out of the woods.
As nearly 900 wildfires continue to burn throughout Canada, experts say the fires and weather patterns like wind direction may change the local air quality going forward.
“Based on the wildfire episodes our city has experienced in the summers of 2023, 2025, and this year, residents should expect periods of changing air quality, depending on Canadian and U.S. West Coast wildfire activity and weather patterns,” said Serap Erdal, associate professor at the University of Illinois Environmental and Occupational Health Sciences School of Public Health.
Late last week, Chicago’s Air Quality Index ranged from very unhealthy to hazardous, the two most severe levels on the Air Quality Index. The conditions were caused by a cold front that carried wildfire smoke to the ground level in Illinois, according to the Environmental Protection Agency.
“Smoke is heavily influenced by the weather,” a spokesperson with the EPA said. “Just as weather can change hour to hour, so can the AQI.”
Generally, an AQI value below 100 is considered acceptable for air quality, while anything over 100 first becomes unhealthy for sensitive groups before becoming unhealthy for everyone as the values increase.
For any value over 301, the air is considered hazardous and all sensitive groups are urged to stay indoors while everyone else is encouraged to avoid lengthy amounts of time outdoors.
As of Tuesday morning, Chicago’s Air Quality Index was around 50, according to the EPA’s AirNow website.
“As air quality improves in the Chicago area, the health risk from wildfire smoke will diminish when AQI levels drop to 100 or lower,” Erdal noted.
The rapidly changing air quality conditions is something Chicago area residents will need to get used to every summer. More intense forest fires in Canada are happening earlier as climate change is producing warmer spring temperatures and dryness up north. Researchers suggest that some of those fires will continue to burn for months, impacting air quality across much of North America.
Fires create fine particulate matter, or PM 2.5, that can lodge deep into your lungs and travel through your blood once inhaled. These microscopic particles are particularly dangerous for people with asthma and other medical conditions or weak immune systems. They can lead to heart attacks and strokes after exposure for long periods.
To avoid health issues due to wildfire smoke, experts stressed the importance of checking the AQI before going outside, staying indoors until the AQI drops to under 100, wearing an N95 or KN95 mask if they need to be outside and setting their air conditioners to “recirculate” mode to ensure outdoor air is not pulled indoors.
“I think everyone should close their doors and windows to try to prevent the smoke from getting into their homes as much as possible,” said Dr. Jack Zhao, a pulmonary critical care doctor at Rush Copley Medical Center. “I equate being outside with a forest fire to smoking. I think over time it will cause long-term side effects.”
Contributing: Brett Chase, Haley Blomquist